1. Field of the Invention
This invention relates to heat transfer mechanisms and more particularly heat transfer mechanisms for removing the heat generated in an electronic circuit module assembly.
2. Related Art
The efficient extraction of heat from electronic circuit modules for very large scale integrated circuit (VLSI) packages has presented a significant limitation on the design and use of such electronic modules. The power consumed in the integrated circuits generates heat which must in turn be removed from the VLSI package. Lacking an efficient heat transfer mechanism, the speed, reliability and power capabilities of the electronic circuit modules are severely limited. As the density of circuits within VLSI chips has increased, the need for improved heat extraction has become even more acute since the more densely packed chips tend to have a higher need for heat dissipation per unit area.
One conventional means of heat extraction has been through the use of a gas encapsulated thermal conduction module of the type described in U.S. Pat. No. 4,266,281. In FIG. 1, there is shown a cross sectional view of a prior art gas encapsulated thermal conduction module 10. The thermal conduction module 10 provides cooling of the integrated circuit chips 12 contained therein. The chips 12 are mounted on one side of a substrate 14, generally made of ceramic, which has pins 16 extending from the other side thereof. The pins 16 provide for the plugging of the module into a board (not shown) which may carry auxiliary circuits, etc. A housing cap 18 is attached to the substrate 14 by means of a flange 20 which extends from the periphery of the substrate 14 to the cap 18. The cap 18 is made of a good heat conductive material such as copper or aluminum. The cap 18 has small cylindrical openings 22 located therein, which are arranged in 3 by 3 arrays directly adjacent to the exposed surface of each chip 12. The openings 22 contain pistons 24 opposite each of the chips 12 in the module. The pistons 24 are made of a good heat conducting material such as aluminum or copper or alloys thereof. The cap 18 is in contact with a cold plate 30 which includes a channel 32 suitable for carrying a fluid coolant such as water.
Each of the pistons 24 has a head or header 26 at the end which contacts the surface of the chip 12 when the pin-piston is inserted into the adjacent opening 22 within the housing 18. A spring 27 is included between the housing 18 and the piston 24 to give a small force of the header 26 against the surface of the chip 12. The force exerted by the spring pressure is such that it will not cause the solder balls 28 on which the chips 12 are mounted to change shape.
In operation, heat generated by the chips 12 is extracted by the headers 26 and conducted by the pistons 24 to the cap 18 and the cold plate 30. As coolant flows through the channel 32, it carries heat away from the cold plate 30, thereby extracting heat from the integrated circuit chips 12 within the thermal conduction module 10. An example of a thermal conduction module is disclosed in U.S. Pat. No. 4,226,281.
While the above-described conduction cooling system has provided a successful solution to date, it is believed that the next generation of VLSI circuits may push pure conduction cooling beyond its ability to efficiently extract heat from the chips. In order to provide cooling solutions for the next generation of chips, it has been proposed to modify the thermal conduction module to use a coolant jet which impinges in a heat sink held against the semiconductor chip which is sealed from the jet. An example of such a proposal is described in IBM Technical Disclosure Bulletin, Volume 29, No. 7, December 1986, Pg. 2887, entitled "LIQUID-COOLED CIRCUIT PACKAGE WITH JET IMPINGING ON HEAT SINK HELD AGAINST SEMICONDUCTOR CHIP THAT IS SEALED FROM THE JET".
One problem with such a solution is that the sealant between the coolant and the semiconductor chips can break down. Since the above-described system is designed for use with a non-dielectric coolant, a breakdown in the seal would allow the coolant to damage the semiconductor chips. Another problem with such a system is that any barrier between the coolant and the chips (such as the sealant itself) will impede heat transfer, thereby impairing some of the benefits which might otherwise be achieved by direct impingment of the jet on the chip.